Watching the trailer for the gliders a big question arose to me.

 

IRL thermal activity mostly depends both on cloud coverage (and of course a multitude of other meteorological parameters) and position of the sun. For simplicity let's assume IRL there is the strongest thermal activity at noon and no thermal activity at midnight.

 

Now that becomes a problem in MSFS because the meteorological paramaters like cloud coverage depend on the weather whereas the position of the sun depends on the time of day (and year) set in the sim. No problem if you fly with the time in sim set to live. But if you set a different time of day in the sim it won't work out.

 

Let's say you want to soar around the Alpes, when in the real world time it is midnight there. You set the time in sim to noon. Will you get the live weather of midnight but with thermals injected related to the position of the sun in the sim? That would completely break the accuracy and plausibility of the injected live weather (you will get strong thermals at low night temperatures). Or will MSFS take the position of the sun in the real world at that time as a basis for the thermals? That would preserve the live weather but would mean that there would be no thermals in the sim even though the sun is high up in the sky in the sim.

 

So there are two alternatives:

Asobo binds the thermals to the weather which means that with live weather they would also have to use the live position of the sun. Otherwise the accuracy and plausibility of live weather would be broken by the different position of the sun in the sim.

Or Asobo binds the thermals somehow to the terrain, taking the position of the sun in the sim as a basis for the thermal activity. That would mean that you would have to use live time in the sim, so that the thermal activity corresponds to the live weather. Otherwise again the accuracy and plausibility of live weather would be broken by the different position of the sun in the sim.

 

Both alternatives mean that you can only reasonably use thermals with the time in sim set to live or with weather presets. Otherwise either the thermal activity would be inadequate related to the position of the sun in the sim or would not correspond to the injected live weather.

 

I wonder how Asobo will be trying to handle this.

 

Do I have to mention that historical weather would solve this issue?

 

 

Edited October 28, 20223 yr by RALF9636

 

I guess these values change based on the current weather in your sim. And the Thermals should hopefully be based on these and the Albedo numbers.

I believe Asobo stated a couple updates ago that the thermals that were added then were dependent on time of day in sim.  This was when some folks started complaining about too much turbulence, and Asobo's response was to fly earlier in the day before the thermals ramped up, or later in the evening. 

So seems likely they'll be tied to time of day in sim.  Works for me...  reported temp doesn't matter much if you don't bother looking at it ;).

Good questions,

my tests revealed a direct relation with Sun radiation and terrain Albedo, but apparently convective potential does not take into account the propeties of the prevailing air mass, such as it's T and lapse rate.

If you use Live Weather but manually set the time to daylight / noon, then the radiation will be there but since they do not appear to take into account the air mass characteristics, inversion layer, etc..., it's a biased calculation.

So, if it's midnight where you want to start your soaring and you're using RWW, and you then set the time to noon, I belive that although you would have a situation of higher instability due to the lower temperatures ( specially if the place has high thermal amplitude ), with the radiation and albedo of terrain generating the thermals, truth is that since MFS only takes into account the calculated radiation, and probably cloud base as well for the limit of the thermal activity, making it possible to simulate blue thermals which is nice in the absence of clouds 🙂 but not being very accurate regarding true convection...

Wonder if inversion layer / limit layer is calculated ?

I believe that unless the true time of day and weather conditions obatined by METAR and forecast are good for soaring, the best is to manually set the weather or use presets for soaring...

The two most advanced soaring simulators, SilentWings and Condorsoaring, use Sun radiation and take into account the geographic coordinates and time of day + date.

SilentWings uses an Albedo-based approach while Condorsoaring uses the concept of "triggers" or "thermal spots" that can be manually set at geographic locations that are known from RL to usually be associated with good thermals.

Idealy MFS or any sim having access to observation and forecast data could use the products the same sources of that data usually have available for soaring.

Soaring Index is one of the "simplest" and is available for instance from meteoblue and windy, as well as some other more sophisticated products:

Windy: Windy.com introduces soaring forecast

I am really looking fwd into feedback from the Gliders update for MFS !!!

Edited October 28, 20223 yr by jcomm

People glide at midnight?  

1 minute ago, bobcat999 said:

People glide at midnight?  

Can be done, in orographic / wave conditions 🙂

21 hours ago, Stearmandriver said:

I believe Asobo stated a couple updates ago that the thermals that were added then were dependent on time of day in sim. 

 

21 hours ago, jcomm said:

my tests revealed a direct relation with Sun radiation and terrain Albedo, but apparently convective potential does not take into account the propeties of the prevailing air mass, such as it's T and lapse rate.

If you use Live Weather but manually set the time to daylight / noon, then the radiation will be there but since they do not appear to take into account the air mass characteristics, inversion layer, etc..., it's a biased calculation.

So, if it's midnight where you want to start your soaring and you're using RWW, and you then set the time to noon, I belive that although you would have a situation of higher instability due to the lower temperatures ( specially if the place has high thermal amplitude ), with the radiation and albedo of terrain generating the thermals, truth is that since MFS only takes into account the calculated radiation, and probably cloud base as well for the limit of the thermal activity, making it possible to simulate blue thermals which is nice in the absence of clouds 🙂 but not being very accurate regarding true convection...

 

 

Thanks for pointing that out. Good to know.

So with the thermals and live weather we will essentially get a mix of historical weather and live weather. The thermal activity will correspond to the time and date set in the sim whereas all other weather parameters will correspond to the current real world weather.

I wonder how that will work out in the sim.

Imagine a cloudless freezing winter night in the current real world (=live weather) and setting mid of summer and noon in the sim. Will there be roaring thermals in the sim at freezing temperatures (Of course there can be thermal activity in winter as well, but it is to be expected a lot weaker than with a higher sun position in summer.)?

 

On 10/28/2022 at 7:11 PM, RALF9636 said:

 

Watching the trailer for the gliders a big question arose to me.

 

So, the question "arose" while you were learning about thermals??  🙂

Another thing is that just going by albedo will not be correct either... Many good thermal generators are nice heat generating surfaces that are covered from wind by a forest or similar in the wind direction, so the hot air gets some nice and quiet growing space. But not too covered as the hot air bubble generated over that nice field need some help to get "ripped off" to not get stuck 🙂

A bit nasty story but anyway... Thermals can be rather unexpected many times and it's very hard to know the source... There was a crematorium near the downwind area of the airfield where I started flying. Some days you got unexpected weak thermals when low there and felt the smell of burning hair at the same time... Helped me at some occasion when too low there. A last helpful hand could be a positive way of seeing it. 

Edited October 29, 20223 yr by mazex

On 10/28/2022 at 5:11 AM, RALF9636 said:

Let's say you want to soar around the Alpes, when in the real world time it is midnight there. You set the time in sim to noon. Will you get the live weather of midnight but with thermals injected related to the position of the sun in the sim? That would completely break the accuracy and plausibility of the injected live weather (you will get strong thermals at low night temperatures). Or will MSFS take the position of the sun in the real world at that time as a basis for the thermals? That would preserve the live weather but would mean that there would be no thermals in the sim even though the sun is high up in the sky in the sim.

So there are two alternatives:

Asobo binds the thermals to the weather which means that with live weather they would also have to use the live position of the sun. Otherwise the accuracy and plausibility of live weather would be broken by the different position of the sun in the sim.

Or Asobo binds the thermals somehow to the terrain, taking the position of the sun in the sim as a basis for the thermal activity. That would mean that you would have to use live time in the sim, so that the thermal activity corresponds to the live weather. Otherwise again the accuracy and plausibility of live weather would be broken by the different position of the sun in the sim.

You raise some good and interesting questions... do have a look at this great thread on the official forums https://forums.flightsimulator.com/t/testing-the-new-airflow-simulation/549454 for lots of details and reports from those testing the SU11 beta right now specifically around the new airflow simulation, thermals, CFD, etc.

The atmospheric airflow movements including thermals are being simulated based on a combination of *all* these factors:

• Position of the sun (Day of year, time of day, location)
• Temperature
• Wind speed
• Clouds
• Albedo (Colors) of the satellite imagery
• Trees
• Water
• Scenery
• Trees
• Terrain slope

So if the sim is set to current time/date and live weather then it would be the most realistic since all the factors are based on current real-world weather factors, time of day/year, etc etc. But if one uses manual time/season setting along with real weather, then of course the airflow simulated is going to be based on that particular combination of factors which would deviate from reality (expectedly). If using manually set time/season and also manually configured weather then again that deviates from reality even more, but also that's to be expected right. Bottom line, whatever combination of time, season, weather, etc that the user configures the sim to use, the factors resulting from that then drives the airflow simulation.

Now one other interesting thing to note is sort of like the "chicken and egg" problem... Given that in the real world there is a direct and bidirectional relationship between clouds and thermals, a sim then has the chicken & egg issue when set to go by real weather (i.e. since rising thermals themselves can influence the formation of clouds)... so in this case, the clouds and other data are being fed in according to the real world (i.e. meteoblue, meta, etc) as one would expect, but then the sim also has to simulate thermals based on all the factors listed above, so when it comes specifically to the thermals-and-clouds relationship, it has to do a "retrofit simulation" where the thermals need to behave accordingly to the clouds injected into the sim, i.e. it's a one-way influence where clouds influences thermals, and not also the other way around. See this other thread on the official forums for some great discussion on this very topic of thermals and clouds interactions, a lot of IRL glider pilots providing their expertise on there too: https://forums.flightsimulator.com/t/6-improved-atmospheric-simulation-with-a-big-focus-on-thermals-and-general-tweaks-for-the-cfd/550009 ... There are some low-cost solutions proposed on that thread which could improve the thermals-influencing-clouds situations which has been logged and noted by Asobo. Short of requiring super-computing resources to provide a full-on weather simulator that also reconciles with real-world weather data, this is a very good first step by MS/ASobo, and unprecedented in what they're trying to achieve compared to other sims.
 

Edited October 29, 20223 yr by lwt1971

11 minutes ago, lwt1971 said:

... Short of requiring super-computing resources to provide a full-on weather simulator that also reconciles with real-world weather data, this is a very good first step by MS/ASobo, and unprecedented in what they're trying to achieve compared to other sims.
 

That's really interesting and sounds very promising.

That would at least mitigate the time of day and time of year issue which exists because of the lack of historical weather.

Now we will get adequate thermal activity corresponding to the time and date in sim even if the live weather corresponds to a different time of day and season.

 

 

 

9 hours ago, mazex said:

A bit nasty story but anyway...

😬 I won't tell the story about trying to scatter ashes from a Stearman.  I like your positive take on your thermal though! 

1 hour ago, Stearmandriver said:

😬 I won't tell the story about trying to scatter ashes from a Stearman.  I like your positive take on your thermal though! 

Well, I have flown in an aircraft where the owner had demanded that his ashes where scattered from the aircraft he loved and had renovated extensively himself with good friends. So I can guess the end result. Let's say he and his beloved 1938 aircraft are one these days. I knew him and I am sure that he would have loved the way it "backfired". An aircraft made of tubes and canvas is very open on the inside with the rear part impossible to access. The only way to "correct the mishap" would have been to re-skin it... His friends that co-owned the aircraft agreed that he would have been the first to day no to that, and laughingly tell the story by the bon-fire after a good day of flying... He's still flying.

Edited October 29, 20223 yr by mazex